1. Field of Invention
This invention relates generally to timepieces, and more particularly to timepieces especially suited for travelers and others experiencing a change of time standards.
2. Description of Prior Art
Present-day personal timepieces, such as wrist and pocket watches, employ a quartz crystal to generate a precise timing signal which is stepped down in frequency to produce trains of timing signals to drive the watch display. In the case of a watch with an analog display, those timing signals drive a step motor which turns the hour and minute hands of the watch. In the case of a watch with a digital display, the timing signal trains control a circuit which drives a LED or liquid crystal display. An electronic watch with an analog display is shown, for example, in U.S. Pat. No. 4,505,594, to Kawahara et al. (1985), while U.S. Pat. No. 4,316,272, to Seikosha (1982) illustrates a watch having a digital display.
A major problem facing people who travel over long distances is adapting to changes in local time caused by their passing through different time zones. This condition is commonly referred to as jet lag. Persons traveling a long distance will often set their watches to the local time upon arrival at the destination. While a person arriving in New York from California may know that the local time is 5:00 P.M., Eastern Standard Time, this person is likely to feel that the "real" time is 2:00 P.M., Eastern Standard Time. This is because the person did not experience a progression in time from the place of departure to the destination location. Thus, after having abruptly set the watch three hours ahead of the current local time of the departure location, the traveler must now attempt to believe that this new local time is the "real" time for him or her. For a long voyage, it often takes a traveler a day or even more to acclimate, both physically and psychologically, to the local time at the new location.
Some present day electronic watches include a function which enables the watch to display local time at various cities in all of the different time zones of the world. Examples of such watches are found in U.S. Pat. No. 4,072,005 to Teshima et al. (1978); U.S. Pat. No. 4,316,272 to Seikosha (1982); and U.S. Pat. No. 4,620,797 to Besson and Meister (1986). A traveler in Boston embarking on a trip to London at 10:00 A.M. may actuate the world time function switch of such a watch and call up London on the watch which will thereupon display the corresponding local time in London, i.e., 3:00 P.M. Thus the traveler becomes aware immediately of the time difference between the two locations. However, this knowledge really does nothing to overcome the jet lag feeling that the traveler will experience upon reaching London. This is because whether the traveler switches the watch to London time upon departing from Boston, while the air over the Atlantic, or upon reaching England, the watch, because it switches between the two local times substantially instantaneously, does not help the traveler to become accustomed psychologically to the new local time.
There does exist a timepiece which changes its time display automatically as it passes from one time zone to the next. This timepiece is described in U.S. Pat. No. 4,204,398, to Lemelson (1980), and includes a radio receiver which responds to signals generated from a remote transmitter located, for example, in the aircraft in which the user is traveling. As the aircraft passes from one time zone to the next, this timepiece can automatically change its display to show the current time in the new time zone. However, this watch does not permit the user to gradually adapt to new time zones. The watch is stepped back or forward in abrupt hourly increments. Further, this watch is quite complex and costly. It supposes that transmitters have been placed which have access to the current local time at any point on the earth. This, too, represents a costly and cumbersome requirement. Consequently, its workings are not practical for incorporation into a relatively low cost personal timepiece, such as a wrist or pocket watch.
Marvosh, in U.S. Pat. No. 4,763,311, describes a double clock, one face of which runs at a fast or slow rate for six months of each year. The purpose of this clock is to gradually alter the user's time standard in order to take advantage of all available daylight throughout the year. It does not address the need for travelers to adapt to an existing time standard.